Over the weekend, a vulnerability in Litecoin's Mimblewimble Extension Block protocol led to a denial-of-service attack against major mining pools, allowing invalid transactions to temporarily bypass nodes that had not been updated. The Litecoin Core v0.21.5.4 release has since been issued, containing critical security updates. According to the Litecoin foundation, the bug has been fully patched and the network is now operating as normal.
However, analysis of the litecoin-project GitHub repository reveals that the consensus vulnerability was privately addressed between March 19 and 26, more than four weeks prior to the attack. A separate denial-of-service vulnerability was also patched on April 25, with both fixes being included in the release 0.21.5.4 after the attack had commenced.
The timeline of events suggests that the attackers may have been aware of the patched and unpatched nodes, exploiting this knowledge to their advantage. Blockchain data indicates that the attacker had pre-funded a wallet 38 hours before the exploit, with the intention of swapping LTC for ETH on a decentralized exchange. The fact that the network was able to automatically handle the 13-block reorganization once the denial-of-service attack ceased implies that a sufficient amount of hashrate was running updated code, ultimately overpowering the attack. This incident highlights the differences in how various networks respond to exploits, with newer chains often coordinating upgrades more swiftly than older proof-of-work networks like Litecoin and Bitcoin.